82 LOCALIZED INFECTIONS OF PUS NATURE 



in reality a coagulum, such as is formed in blood clotting, 

 but without red-blood cells; it may be a tenacious covering 

 of a surface called a false membrane, such as is seen on a 

 diphtheritic throat, more or less closely adherent to the sur- 

 face from which it arises; it may possess special characters, 

 such as hemorrhagic when much blood is admixed, or mucoid 



when it resembles mucus. 



. I 



PUS-PRODUCING MICROORGANISMS. 



It has been stated that there is no particular germ always 

 responsible for pus, but some varieties of the round bacteria 

 are the commonest causes. They are called micrococci or 

 staphylococci and streptococci. Certain members of the 

 group of cocci may also do other things than produce simple 

 pus or abscesses. These will be considered at the end of this 

 chapter. Bacteria other than cocci which can produce pus are 

 the colon bacillus, pyocyaneus bacillus, and typhoid bacillus. 



FIG. 26. Staphylococcus. X 1100 diameters. (Park.) 



Staphylococcus Pyogenes Aureus. Of the micrococci there 

 is one particular species of importance which by some bac- 

 teriologists has been divided into two varieties because 

 members of the group differ in their ability to produce color 

 in laboratory cultures and because the one having a golden- 

 yellow pigment is somewhat more frequently found in pus. 



